So-called “stoppings” are widely used in mines to stop off the flow of air in passages in the mines, a “stopping” traditionally being a masonry (e.g., concrete block) or metal wall installed at the entrance of a passage to block flow of air therethrough. This invention relates especially, albeit not exclusively, to the type of metal mine stopping shown for example in U.S. Pat. No. 4,483,642 (Re. 32,675) comprising a plurality of elongate extensible panels extending vertically in side-by-side relation from the floor to the roof of a mine passage across the width of the passage. After the panels are installed, there are gaps between the panels and between the panels and adjacent surfaces of the mine (i.e., the floor, the roof and the ribs defining opposite sides of the passage). These gaps are typically sealed in a number of ways, as by spraying a foam, such as a polyurethane foam, on the stopping and around the stopping. However, when there is shifting and heaving of the mine in the vicinity of the passage (sometimes referred to as a “mine convergence”), sprayed-on foams tend to buckle away from the surfaces, exposing cracks. Cementitious sealants are also used, but mine convergence often causes the sealant to pop off the surfaces. More flexible sealants are sometimes used as well, but these are easily torn by relative movement of the panels, and they add no strength to the stopping.
U.S. Pat. No. 6,419,324 discloses a method of sealing a mine stopping by injecting a foaming material under pressure into the gaps between the vertical mine stopping panels to form a seal between adjacent panels. The '324 patent also describes spraying the foam in a line along the periphery of the stopping to fill or at least cover gaps between the stopping and the mine surfaces.
The present inventors have made various improvements in this field, which will be described in detail below.